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A Dog HistoryThe dog (Canis lupus familiaris) is a domesticated subspecies of the wolf, a mammal of the Canidae family of the order Carnivora. The term encompasses both feral and pet varieties and is also sometimes used to describe wild canids of other subspecies or species. The domestic dog has been one of the most widely kept working and companion animals in human history, as well as being a food source in some cultures. There are estimated to be 400 million dogs in the world.

The dog has developed into hundreds of variedbreeds. Height measured to the withers ranges from a few inches in the Chihuahua to a few feet in the Irish Wolfhound; color varies from white through grays (usually called blue) to black, and browns from light (tan) to dark ("red" or "chocolate") in a wide variation of patterns; and, coats can be very short to many centimeters long, from coarse hair to something akin to wool, straight or curly, or smooth.

OriginsBased on DNA evidence, the wolf ancestors of modern dogs diverged from other wolves about 100,000 years ago and dogs were domesticated from those wolf ancestors about 15,000 years ago. This date would make dogs the first species to be domesticated by humans.

Evidence suggests that dogs were first domesticated in East Asia, possibly China and some of the peoples who entered North America took dogs with them from Asia.

As humans migrated around the planet a variety of dog forms migrated with them. The agricultural revolution and subsequent urban revolution led to an increase in the dog population and a demand for specialization. These circumstances would provide the opportunity for selective breeding to create specialized working dogs and pets.

Ancestry and history of domesticationMolecular systematics indicate that the domestic dog (Canis lupus familiaris) descends from one or more populations of wild wolves (Canis lupus). As reflected in the nomenclature, dogs are descended from the wolf and are able to interbreed with wolves.

The relationship between human and canine has deep roots. Converging archaeological and genetic evidence indicate a time of domestication in the late Upper Paleolithic close to the Pleistocene/Holocene boundary, between 17,000 and 14,000 years ago. Fossil bone morphologies and genetic analysis of current and ancient dog and wolf populations have not yet been able to conclusively determine whether all dogs descend from a single domestication event, or whether dogs were domesticated independently in more than one location. Domesticated dogs may have interbred with local populations of wild wolves on several occasions (a process known in genetics as introgression).

The earliest dog fossils, two crania from Russia and a mandible from Germany, date from 13,000 to 17,000 years ago. Their likely ancestor is the large northern Holarctic wolf, Canis lupus lupus. Remains of smaller dogs from Mesolithic (Natufian) cave deposits in the Middle East, dated to around 12,000 years ago, have been interpreted as descendants of a lighter Southwest Asian wolf, Canis lupus Arabs. Rock art and skeletal remains indicate that by 14,000 years ago, dogs were present from North Africa across Eurasia to North America. Dog burials at the Mesolithic cemetery of Svaerdborg in Denmark suggest that in ancient Europe dogs were valued companions.

Genetic analyses have so far yielded divergent results. Vilà, Savolainen, and colleagues (1997) concluded that the ancestors of dogs split off from other wolves between 75,000 and 135,000 years ago, while a subsequent analysis by Savolainen et al. (2002) indicated a "common origin from a single gene pool for all dog populations" between 40,000 and 15,000 years ago in East Asia. Verginelli et al. (2005), however, suggest both sets of dates must be reevaluated in light of recent findings showing that poorly calibrated molecular clocks have systematically overestimated the age of geologically recent events. On balance, and in agreement with the archaeological evidence, 15,000 years ago is the most likely time for the wolf-dog divergence.

The Soviets have attempted to domesticate the fox, mentioned in the article Tame Silver Fox, and were able to do so in just nine generations, or less than a human lifetime. This also resulted in other changes, including color, which became black, white, or black and white. They also developed year-round breeding ability, curled-up tails, and droopy ears.

The rapidity of this change has suggested to researchers a scenario of the origin of the domestic dog. Primitive people lived on the edge of survival which involved occasional food shortages, and would not have taken wolf pups and made pets of them. However, wolves would raid garbage dumps near human habitations. Wolves have a flight distance which they keep between themselves and a threatening creature. When a dump was approached by humans, some wolves would run a greater distance from the dump than others. Those that ran the shortest distance would return first, and obtain the greatest amount of food.

This set up a selective breeding situation that resulted in a strain of wolves having shorter and shorter flight distances, until they were eventually comfortable near humans, having domesticated themselves, so to speak. At that point, they were tolerated by humans, so long as they were also useful, in such ways as catching rats or driving away other predators. In time, other uses, such as hunting, were found for them.(continued on BOOKS page)